This invention relates to a vibration restraining apparatus for a vehicle attached to a vibration transmitting member to restrain a harmful vibration occurring therein. Here, the vibration transmitting member includes a suspension arm, sub frame, body panel, engine mounting bracket, engine unit or exhausting device of an automobile, and an arm member or a body panel of an electric train.
A running vehicle such as an automobile for example generates a vibration by operation of an engine as a power source, and the generated vibration is inputted into the road through surface during running of the vehicle. These vibrations are in turn transmitted to the vehicle body through an engine mounting bracket or a vehicle body frame supporting an engine unit or a suspension arm or sub frame connected to wheels. If a natural resonance occurs in these vibration transmitting members, the vibration transmission to the vehicle body is amplified to cause noise in the vehicle room and vibration of vehicle frame.
In view of the above, in the prior art, the vibration occurred in those vibration transmitting member is restrained or damped by attaching a mass damper, dynamic damper or a vibration restraining member.
The above mass damper is constructed by adding a mass (weight) to the vibration transmitting member, so that the natural vibrating frequency of the vibration restraining member is varied, thus restraining a target vibration. However, more mass needs to be added for obtaining sufficient vibration restraining effect by the mass damper, which increases the weight of the mass damper.
Also, the above dynamic damper is a vibration absorbing apparatus constructed by a portion attached to the vibration transmitting member, a mass (mass body) disposed apart from the attach portion, a rubber elastic body (spring) disposed between the mass and the attached portion and connects them integrally. This dynamic damper is attached to the vibration transmitting member at an attached portion thereof to reduce amplitude of the vibration transmitting member by resonance of the mass/rubber elastic body in resonances of the vibration transmitting member in resonance vibration.
However, the resonance frequency of this dynamic damper is determined based on weight of the mass body and spring constant of the rubber elastic body, so the dynamic damper can restrain the vibration at only one frequency area in the resonance occurred in the vibration transmitting member, but is not effective with respect to plural resonances. Also, the weight of the mass body and the spring constant of the rubber elastic body are set based on applying a direction of them (vibration direction) determined by the positional relation between the mass body and the rubber elastic body, and therefore have directionality. Accordingly, restraining the vibrations in many directions simultaneously by one dynamic damper is difficult. Also, the spring constant of the rubber elastic body used as the spring easily varies depending on temperature and has a large temperature dependency, so that the vibration restraining effect is deteriorated at a high temperature and at a low temperature.
The above vibration restraining member is formed like a sheet by single layer or plural layers made of asphalt, urethan, acrylic resin or metallic plate, and is adhered to a surface of the panel-like vibration transmitting member such as a roof panel or floor panel for use. The vibration restraining member deforms elastically corresponding to resonance of the vibration transmitting member to absorbs a vibrating energy of the vibration transmitting member by an internal friction generated at that time, thereby damping resonance of the vibration transmitting member.
However, such vibration restraining member needs to be adhered to the vibration transmitting member in rather broad area, and has larger weight due to a forming material of relatively large specific gravity. In addition, due to the temperature dependency of the vibration restraining member, the vibration restraining effect may be decreased at a high temperature and low temperature when the vibration restraining member is tuned at the room temperature.
Thus, the mass damper, dynamic damper and vibration restraining member which have been conventionally used have above problems.
The present invention is made in view of the above circumstances and has a subject matter or purpose to provide a vibration restraining apparatus for vehicle which can be lightened in weight, does not have the temperature dependency, and can perform the vibration restraining effect for plural resonances having different frequencies.
A vibration restraining apparatus of the present invention is featured by a housing made of a rigid material and having an inner space, and fixed to a vibration transmitting member; and a filled member sealed in the inner space of the housing in a non-adhered state with leaving a gap with respect to a vibrating direction of the housing, and formed by an elastic body at least at a surface thereof.
In this vibration restraining apparatus for vehicle, when the housing resonates by the vibration transmitted from the vibration transmitting member, the filled member contacts (abuts) with (onto) inner surfaces of the housing at both sides in the vibrating direction, so that the damping character of the filled member relative to the housing due to an energy loss caused by a sliding friction and a collision is exercised. In this way, the large damping character occurs inside the housing to restrain the vibration of the housing effectively. As a result, the vibration of the vibration transmitting member is effectively restrained.
In the vibration restraining apparatus for vehicle of the present invention, the damping character is exercised based on the energy loss caused by the sliding friction and the collision generated when the filled member constants (abuts) with (onto) the inner surface of the housing, so the damping character can be exercised for plural resonances of different frequencies. Also, the vibration damping operation does not have the temperature dependency since the amount of the loss energy due to the sliding friction and the collision is hardly affected by the temperature.
In addition, in the vibration restraining apparatus for vehicle, since the gap formed between the inner surface of the housing and the filled member can be freely set corresponding to a vibrating direction of the housing (vibrating direction of vibration transmitting member), the vibration in the all directions of the housing can be restrained.
Here, when the housing is lightened, vibration of the housing may increase corresponding to a decrease in inertia if the inputted vibration is constant. However, the vibration is damped by disposing the filled member in the inner space of the housing by leaving the gap in the vibration restraining apparatus for a vehicle of the present invention, so lightening of the housing can be realized without worsening the vibration.
Accordingly, the vibration restraining apparatus for vehicle can be lightened, does not have the temperature dependency, and can exercise the vibration restraining effect for plural resonances of different frequencies. Here, the vibration restraining apparatus for vehicle of the present invention can be attached to all kinds of the vibration transmitting members of the vehicle to restrain the vibration thereof satisfactorily.
The vibration restraining apparatus for vehicle of the present invention can be embodied by various means or modes to be explained below.
That is, the housing of the present invention is formed by a rigid material and has a closed inner space therein. As the rigid material for forming the housing, metals such as an iron or an aluminium alloy etc. or a hard resin can be adopted, for example. These rigid materials preferably have an elasticity rate more than 5xc3x97104 MPa. If the elasticity rate is smaller than 5xc3x97104 MPa rigidity of the housing becomes insufficient, so that shape of the gap to be formed between the inner surface of the housing and the filled member sealed in the inner space may be unstable.
The housing can have an optional shape such as a circular tube or a square tube, and can be linear, bent or curved.
Here, when the vibration transmitting member is an arm member for vehicle of hollow shape having an inner space such as a suspension arm for example, this arm member can be used as the housing. Also, by forming an inner space in the vibration transmitting member to attach the vibration restraining apparatus for vehicle therein, the vibration transmitting member can be used as the housing. This housing can be formed so as to be integral with the vibration transmitting member, which makes attaching working of the vibration restraining apparatus for vehicle to the vibration transmitting member unnecessary.
In addition, the housing can be constructed to have a bracket for fixing the vibration restraining apparatus to the vibration transmitting member.
A plurality of inner spaces can be provided in the housing by forming partitioning walls. For example, in case where the housing is formed by an extrusion-formed body, the partitioning walls extending along an extruding direction can be easily formed in the extrusion-forming. By formation of plural inner spaces into which the filled members are sealed, the vibration restraining effect can be increased.
The filled member of the present invention is sealed into the inner space of the housing in a non-adhered state with leaving the gap with respect to the vibrating direction of the housing. That is, the filled member is disposed in the inner space so as to be freely moved. The filled member can have a plane, a curved surface, or a convex/concave shape. In summary, the gap existed between the surface of the filled member and the inner surface of the housing is sufficiently formed at a surface part of the filled member most protruded.
The minimum gap rate of the gap formed between the housing and the filled member is preferably selected smaller than 30%. If the minimum gap rate is more than 30%, when the housing vibrates in particularly small amplitude, the filled member hardly contacts (abuts) with (onto) the inner surface of the housing located at both sides in the vibrating direction, so that satisfactory vibration restraining effect is not exercised. Here, xe2x80x9cminimum gap ratexe2x80x9d is calculated, in a state where one surface of the filled member is contacted with the inner surface of the housing, by dividing distance dimension of the gap formed between the most protruded part of the filled member at the other end and the opposing inner surface of the housing by distance dimension between the opposed inner surfaces of the housing.
The gap formed between the housing and the filled member preferably has a length dimension of 0.1 to 0.5 mm. If the gap dimension is smaller than 0.1 mm the filled member hardly moves in the inner space of the housing, so that the energy transferring due to contact (abutment) of the filled member with (onto) the housing decreases, which results in poor or insufficient vibration restraining effect. To the contrary, if the gap dimension is more than 0.5 mm, a loud noise may be generated when the filled member contacts (abuts) with (onto) the housing.
The filled member of the present invention is not necessarily disposed over the whole area of the housing in a longitudinal direction thereof even when the housing has a longitudinal shape, but may be locally or partially disposed at a portion of the housing where the vibration is generated particularly.
In addition, the filled member of the present invention is formed by an elastic body at least at a surface thereof. If surface of the filled member is formed by the rigid material, the colliding sound or noise may occur when the filled member contacts (abuts) with (onto) the inner surface of the housing. For this reason, the surface portion of the filled member preferably has a hardness value smaller than shore D hardness 80. As the elastic body forming at least the surface of the filled member, a rubber, resin or elastic foamed body formed by the rubber and the resin as the main components can be adopted. Such elastic body preferably has characteristics such that the compression elasticity rate thereof is 1 to 104 MPa, and tan xcex4 (loss tangent) is more than 103, preferably 0.01 to 10.
As the resin, a fiber reinforced resin (FRP) having an elasticity rate more than 103 can be adopted. The elastic foamed body suitably adopted is formed by foaming a filled member forming material including at least one of the rubber and the resin, and the foaming agent as the main component.
In addition, as the rubber utilized, a high specific gravity rubber having a density of more than 1.5 g/cm3 can be suitably adopted. If the density thereof is smaller than 1.5 g/cm3 the volume of the rubber becomes large to obtain the desired weight of the filled member, thus above high specific gravity rubber being effective to omit a surplus space. This high specific gravity rubber can be formed, for example, by adding a filling agent for high specific gravity such as a metal powder (iron, tungsten) or a metal oxide powder (zinc oxide, lead oxide etc.) to a polymer such as a natural rubber (NR) or an ethylenepropylene-diene ternary copolymer (EPDM). The high specific gravity rubber having density of 2.0 g/cm3 can be obtained by adding the zinc oxide of 250 weight parts to the natural rubber of 100 weight part. To the high specific gravity rubber, various adding agents such as a vulcanizing agent, an aging preventing agent, a working promoting agent or a plasticizer can be added.
When the vibration restraining apparatus for vehicle of the present invention is used in a high temperature environment, the high specific gravity rubber preferably has the heat resistance character that a tension strength change after aging in 120xc2x0 C.xc3x9770 hours is less than 50%. Such high specific gravity rubber can be formed by using an olefin series thermoplastic elastmer (TPO) or a styrene series thermoplastic elastmer (TPS) as the polymer, and using a barium sulfate etc. as the filled member for high specific gravity. In this case, the high specific gravity rubber having the density of 2.0 g/cm3 can be formed by selecting the weight ratio of the TPO and the barium sulfate 100:230, and that having the density of 3.0 g/cm3 can be formed by selecting the weight ratio of the TPO and the barium sulfate 100:770.
The filled member of the present invention can be formed by a single member having size so that a gap is formed between the filled member and the housing when it is inserted into the inner space. Also, when the above elastic foamed body is used as the filled member, the filled member can be disposed in the inner space by foaming a filled member forming material in the inner space. In this case, the elastic foamed body (filled member) foamed and A formed in the inner space of the housing can form the gap between the filled member and the housing by utilizing a thermal shrinkage after the foaming. Thus, according to this method, at the time when the filled member forming material foamed in the inner space of the housing the elastic foamed body is filled and disposed in the inner space, whereby a working main-hour can be reduced and simplified.
As the rigid material forming other part except for the surface part an optional material such as a metal, a hard resin or a stone can be suitably adopted.
In addition, the filled member of the present invention is not necessarily formed into the solid shape, but can be formed into a tubular or cylindrical shape both ends of which are opened, or can have a closed space therein. The tubular shape and the closed space can reduce using material amount of the filled member to lighten weight of the filled member.
Further, when the filled member is formed into the tubular shape, it can have a constraining layer at an inner periphery thereof. According to this construction, the constraining layer constrains an elastic deformation of the elastic body forming the surface part of the filled member, so that more sliding and more collision of the filled member relative to the housing are obtained, which is convenient to restrain the vibration more securely. This constraining layer can be constructed for example by a film formed by a metal or a resin.